1. Field of the Invention
The present invention relates to seals for use as construction elements. Such seals can be used to intrinsically seal construction elements or to seal the assembly of a plurality of adjacent elements to form a wall.
The invention relates more particularly to seals for insulating wall panels, often called sandwich panels. These types of panels consist of metal walls delineating a cavity filled with a materially having good thermal and/or acoustic insulation properties such as a rigid foam of a polymer such as polyurethane. Such panels are advantageous in that they combine rigidity, lightness and high thermal/acoustic performance.
2. Discussion of the Background
Such panels are generally manufactured in the following manner. Continuous sheet-metal sheets are placed horizontally facing each other. These sheets are held at a given distance from each other while they move progressively on a conveyor belt. A highly reactive liquid mixture is then injected between these metal sheets. The liquid mixture expands in every direction in the form of a polymer foam. In order to prevent this foam from spilling out, the rims of the metal sheets are fitted with seals.
Once the foam has completely expanded, the metal sheets are cut transversely in order to obtain panels of the desired length. These panels can be subsequently joined together side-by-side to form walls, partitions, ceilings, etc. The seals, which initially served to contain the expansion of the foam within the cavity defined by the metal sheets, can also be used to seal at the grouting areas between adjacent panels. These seals protect the walls against moisture and prevent the creation of a thermal bridge when these panels are used outdoors.
In order to be effective, the seals must meet certain criteria. First, they must have good flexibility and good compressibility. Thus, seal; are themselves usually based on a polymer foam. The seals must also allow good "keying" and provide good adhesion to the panel cavity foam. These criteria are difficult to attain if the exterior of the seals are too smooth--which is often the case when the seals are made of closed-cell foam.
In order to remedy this, the industry has attempted two solutions--each with its; own drawbacks. First, the surface of the seal intended to be in contact with the panel foam may be roughened by abrading or slitting the foam of the seal along its thickness. Such methods are complicated and generate dust which subsequently has to be eliminated. Alternatively, the seal may also be rendered adhesive by incorporating an adhesive (for example of the acrylic type) into the foam. However, the presence of plasticizer in the seal may decrease its bondability to the interior foam. Furthermore, adhesives are combustible and may increase the flammability of the panels.
Typically, metal sheets retard the spread of fire. Unfortunately, their grouting areas are weak points. If the seals used to seal the grouting areas are flammable and they are directly exposed to flame, the fire may spread laterally, through the seals to the interior foam of the panels.